This invention relates in general to imaging, and more specifically to a new migration imaging system.
There has recently been developed a migration imaging system capable of producing high quality images of high density, continuous tone, and high resolution, an embodiment of which is described in my copending application Ser. No. 460,377, filed June 1, 1965. Generally, according to an embodiment thereof, an imaging member comprising a substrate with a layer of softenable material, containing photosensitive particles, overlying the substrate is imaged in the following manner: a latent image is formed on the member, for example, by uniformly electrostatically charging and exposing it to a pattern of activating electromagnetic radiation. The imaging member is then developed by exposing it to a solvent which dissolves only the softenable layer. The photosensitive particles which have been exposed to radiation migrate through the softenable layer as it is softened and dissolved, leaving an image of migrated particles corresponding to the radiation pattern of an original, on the substrate with the material of the softenable layer substantially completely washed away. The particle image may then be fixed to the substrate. For many preferred photosensitive particles, the image produced by the above process is a negative of a positive original, i.e., particles deposit in image configuration corresponding to the radiation exposed areas. However, positive to positive systems are also possible by varying imaging parameters. Those portions of the photosensitive material which do not migrate to the substrate are washed away by the solvent with the softenable layer. As disclosed therein, by other developing techniques, the softenable layer may at least partially remain behind on the supporting substrate.
In general, three basic imaging members may be used: a layered configuration which comprises a substrate coated with a layer of softenable material, and a fracturable and preferably particulate layer of photosensitive material at or embedded near the upper surface of the softenable layer; a binder structure in which the photosensitive particles are dispersed in the softenable layer which overcoats a substrate; and an overcoated structure in which a substrate is overcoated with a layer of softenable material followed by an overlayering of photosensitive particles and a second overcoating of softenable material which sandwiches the photosensitive particles. Fracturable layer or material as used herein, is intended to mean any layer or material which is capable of breaking up during development and permitting portions to migrate towards the substrate in image configuration.
The imaging system of 460,377 generally comprises a combination of process steps which include forming a latent image and developing with solvent liquid or vapor, or heat or combinations thereof to render the latent image visible. In certain methods of forming the latent image, non-photosensitive or inert, fracturable layers and particulate material may be used to form images, as described in copending application Ser. No. 483,675, filed Aug. 30, 1965, wherein a latent image is formed by a wide variety of methods including charging in image configuration through the use of a mask or stencil; first forming such a charge pattern on a separate photoconductive insulating layer according to conventional xerographic reproduction techniques and then transferring this charge pattern to the imaging member by bringing the two layers into very close proximity and utilizing breakdown techniques as described, for example, in Carlson U.S. Pat. No. 2,982,647 and Walkup U.S. Pat. Nos. 2,825,814 and 2,937,943. In addition, charge patterns conforming to selected, shaped, electrodes or combinations of electrodes may be formed by the "TEST" discharge technique as more fully described in Schwertz Patents 3,023,731 and 2,919,967 or by techniques described in Walkup Patents 3,001,848 and 3,001,849 as well as by electron beam recording techniques, for example, as described in Glenn Pat. No. 3,113,179.
In another variation of the imaging system of 460,377, an image is formed by the selective disruption of a particulate material overlying or in an electrostatically deformable, or wrinklable film or layer. This variation differs from the system described above in that the softenable layer is deformed in conjunction with a disruption of the overlayer of material as described more fully in copending application Ser. No. 695,074, filed Jan. 2, 1968 now U.S. Pat. No. 3,542,545.
The characteristics of the images produced are dependent on such process steps as charging, exposure and development, as well as the particular combination of process steps. High density, continuous tone and high resolution are some of the image characteristics possible. The image is generally characterized as a fixed or unfixed particulate image with or without a portion of the softenable layer and unmigrated portions of the layer left on the imaged member, which can be used in a number of applications such as microfilm, hard copy, optical masks, and strip out applications using adhesive materials.
As disclosed in 460,377 and 483,675 and as further elaborated on herein, the layer of softenable material of the imaging member in some developing techniques is (a) substantially completely washed away (washaway development) and by other developing techniques (b) (softening development) may at least partially remain behind on the supporting substrate. The invention hereof is intended to encompass both (a) and (b) and indeed any and all suitable developing and softening techniques.
460,377 and 483,675 are hereby expressly incorporated by reference herein principally because of their ample teachings of washaway development and also their teachings of softening development where the softenable layer completely or partially remains after development herein. Especially softening development is elaborated on herein.
It will be seen that the invention hereof encompasses optimum electrical-optical modes of migration imaging, wherein latent images are formed by modes similar to those described in 460,377, preferred modes employing electrical migration forces associated with electrostatic images, optionally with a radiation exposure step, wherein latent images are formed by modes similar to those described in 483,675, as well as other novel and advatageous imaging modes wherein optical exposures are not necessary for imaging and wherein migration forces other than electrical forces are used as a migration force.